The finding (Spizizen, 1958(Spizizen, , 1959) that a number of auxotrophic mutants of Bacillus subtilis could be transformed to prototrophy has provided a simple system for the study of transformation of biochemical characters. This is made possible by the fact that B. subtilis can be grown

Current microfluidic paper-based devices lack crucial components for fluid manipulation. We created a fluidic diode fabricated entirely on a single layer of paper to control the wicking of fluids. The fluidic diode is a two-terminal component that promotes or stops wicking along a paper channel. We further constructed a trigger and a delay valve based on the fluidic diode. Furthermore, we demonstrated a high-level functional circuit, consisting of a diode and a delay valve, to manipulate two fluids in a sequential manner. Our study provides new, transformative tools to manipulate fluid in microfluidic paper-based devices.

The etfects on transformation and transduction of an ultraviolet sensitivity (ul') and two ultraviolet sensitivity-recombination deficiency (rec-land rec-2) mutations in isogenic strains of Bacillus slibtilis were investigated. Transformation frequency in the rec-land rec-2 § strains was reduced to approximately 5 and 25 %-, respectively, of the parental strains. Normal kinetics of deoxyribonucleic acid dose response in transformation were found for the rec-l+ and rec-2-strains. Biphasic curves were obtained with the rec-lstrains. Transduction frequency with bacteriophage SP-10 decreased parallel to transformation frequency in the rec-1and rec-2-T strains. This result suggests that transformation and SP-10 transduction share a common mechanism for genetic recombination. It also indicates that the reduction in transformation frequency of these strains was not due to altered competence. Transduction frequency with bacteriophage PBS-1 or 3NT, on the contrary, was not diminished in rec-lstrains. This frequency was reduced in rec-2strains but not as severely as that of transformation or SP-10 transduction. Several hypotheses to interpret these differences are presented. Recombination frequency between linked markers was reduced more than 50c' in transformation by the presence of the rec-l mutation. Linkage was unaffected in the rec-27 strains. Neither the rec-1-k nor the rec-2mutation had an effect on linkage in PBS-1 or 3NT transduction. The uvr-strains were transformed at a frequency equal to or greater than that of the parental strains. These strains were transduced by all bacteriophage systems at frequencies about twofold higher than those of parental strains. The similarity between the process of repair of ultraviolet (UV) irradiation-damaged deoxyribonucleic acid (DNA) and that of genetic recombination was first postulated by Howard-Flanders and Boyce (13). They suggested that '} These strainis were obtainied througlh the kindness of Ken Bott, The University of Chica,o. ConIstruwIctetCC bV transformationi. The hea(l of the arrow indicates the recipicnt strain. 1926 J. BACH RIOL.

No abstract

Currently, the Lateral flow Immunoassays (LFIAs) are not able to perform complex multi-step immunodetection tests because of their inability to introduce multiple reagents in a controlled manner to the detection area autonomously. In this research, a point-of-care (POC) paper-based lateral flow immunosensor was developed incorporating a novel microfluidic valve technology. Layers of paper and tape were used to create a three-dimensional structure to form the fluidic network. Unlike the existing LFIAs, multiple directional valves are embedded in the test strip layers to control the order and the timing of mixing for the sample and multiple reagents. In this paper, we report a four-valve device which autonomously directs three different fluids to flow sequentially over the detection area. As proof of concept, a three-step alkaline phosphatase based Enzyme-Linked ImmunoSorbent Assay (ELISA) protocol with Rabbit IgG as the model analyte was conducted to prove the suitability of the device for immunoassays. The detection limit of about 4.8 fm was obtained.